Unit 1: Understanding of Large Numbers
Number of digits: unit, ten, hundred, thousand, ten, hundred, million, ten, billion, billion, billion …
Counting unit: unit, ten, hundred, thousand, ten thousand, one hundred thousand, one million, ten million, one billion, ten billion, one hundred billion …
Every four digits are one level. Divided into 10, 1 10,000, 1 100 million.
Level is how many ones, level is how many tens of thousands, level is how many billions.